Music and architecture share not only phenomenological similarities in relation to their characteristics - like volume, timbre, tone pitch, instrumentation vs. geometry, materiality, light ambiance or perspective - but imply as well comparability in the process of creation. The investigation of digital tools that cross borders between music and architecture was the starting point for the research project “Mixer Modellingi. Against this background the paper discusses the transformation of a musical composition controller into an intuitive design tool for the generation of architectural geometries. In the same amount that the use of a MIDI-controller increases the degrees of freedom for the simultaneous activation of various parameters the definition of geometric dependencies on the level of visual programming become more important for the resulting geometry.